Some compound nouns function as one grammatical unit even though written in two parts.
حَضَرَ أَحَدَ عَشَرَ رَجُلًا. — Eleven men attended.
Aḥada ʿashara: compound numeral built on fatḥa in both parts, in nominative position as subject; rajulan: accusative tamyīz.
A word can be built yet occupy a nominative position.